1. Field of the Invention
This invention relates to an ink jet apparatus for discharging ink from recording means to a recording medium to thereby effect recording, and particularly to an ink jet apparatus provided with a mechanism for achieving recording of higher quality.
2. Related Background Art
Recording apparatuses having the function of a printer, a copying machine, a facsimile apparatus or the like, or recording apparatuses used as compound machines including a computer and a word processor or the output apparatuses of work stations are designed such that a sheet-like recording medium such as paper or a plastic sheet is fed and conveyed and images are successively recorded on the recording medium on the basis of recording information. Such recording apparatuses can be grouped into the ink jet type, the wire dot type, the thermal type, the laser beam type, etc., depending on their recording systems.
Among them, the ink jet type (ink jet recording apparatus) is one which discharges ink from recording means (a recording head) to a recording medium to thereby effect recording, and has merits that it can record highly accurate images at a high speed, that it produces little noise because of it being a non-impact system and that inks of multiple colors can be used to record colored images easily. Also, as scanning systems for the recording means, use is usually made of a serial system using both of main scanning for moving the recording means along the recording medium and sub-scanning for moving the recording medium in the direction of conveyance, and the line system using recording means of the line type in which a number of discharge ports are arranged in the widthwise direction of paper and effecting only sub-scanning.
Particularly, as regards recording means (a recording head) of the ink jet type which utilizes heat energy to discharge ink, one having a liquid path arrangement (discharge port arrangement) of high density can be easily manufactured by forming an electro-thermal conversion member, an electrode, liquid path walls, a top plate, etc. made by filming on a substrate by way of the semiconductor manufacturing process including etching, vapor deposition, sputtering, etc. On the other hand, there are various requirements for the material of the recording medium, and in recent years, it has become required to use, besides paper and resin sheets (such as OHP) which are ordinary recording mediums, thin paper and worked paper (such as punched paper for filing, perforated paper and paper of any shape).
In the above-described ink jet recording apparatus, splashes of ink or the like are created when the ink is discharged from the recording head (recording means). Particularly, where a plurality of recording heads are used as during color recording, the quantity of splashes of ink is liable to become greater and the possibility of the splashes adhering to the surfaces of discharge ports, including the other recording heads is high, and the adherence of the splashes may deviate the directionality of discharged ink or the splashes adhering to said surfaces may be increased in viscosity to thereby clog the discharge ports, thus adversely affecting ink discharge and deteriorating the quality of images. Also, in some cases, under the influence of the adhering splashes, foreign materials such as paper powder and dust may adhere to said surfaces of the discharge ports and again in such cases, ink discharge is adversely affected. So, cap means for covering the surfaces of the recording heads during the non-use of the heads is provided with a view to continuously effect good recording, or a cleaning member such as a blade is provided to wipe off ink or foreign materials such as dust adhering to the surfaces of the discharge ports of the recording heads.
Now, ink jet apparatuses include apparatuses in which a plurality of recording heads (yellow, cyan, magenta and black) are provided to enable full color recording to be accomplished as previously described. In such apparatuses, full color recording is usually effected, but in some cases, recording using only a predetermined color (e.g. black) is effected.
Even in such a case, the recording heads which do not contribute to recording are also scanned because the plurality of recording heads are usually carried on a common carriage.
Thus, due to such scanning, splashes of ink may adhere to the surfaces of the recording heads which do not contribute to recording or foreign materials such as dust and paper powder may adhere to said surfaces.
The recording heads to which foreign materials adhere may in some cases exhibit the deterioration of their ink discharging performance as previously described and therefore, they are cleaned by a cleaning member or the like. The cleaning of the recording heads which are not used for recording may result in the peeling of the water repelling agent, the movement of unnecessary materials from the cleaning member, etc, and thus will affect the recording heads in one way or another.
Accordingly, it is preferable to design the recording heads such that only the recording head being used is cleaned. It is also preferable that only the head used be scanned. However, the head used entirely differs depending on recorded images and therefore, the design for only the recording head used to be scanned independently is very complicated and cannot be achieved unless difficult control is resorted to.
In researching to solve the above-noted problems it has been found that if during the recording scan of the carriage on which the recording heads are carried, those of the recording heads which are not used in the recording of that one line are retracted so as to be spaced apart from the recording position, it is difficult for splashes of ink to adhere to the surfaces of those heads.
The present invention has been made on the basis of this finding.
Also, the present invention will suffice if it achieves the technical idea of retracting the recording heads from an area in which ink are liable to adhere to the surfaces of the heads during recording are floating, or preventing ink droplets from adhering to the surfaces of the recording heads or making it difficult for ink droplets to adhere to the surfaces of the recording heads, by some other technique.
This technical idea can be achieved not only by the design for retracting the unnecessary recording heads from the recording station during recording scan, but also by a design for retracting all heads during return.
Also, a cover may be provided over the surfaces of the recording heads which are not used for recording. Of course, such covering may be done at the recording position of the recording heads, but when it is taken into account that the spacing between the surfaces of the heads and the recording medium is very small, the covering may preferably be done after the recording heads which are not used for recording are retracted to provide a predetermined or greater spacing so that the cover may not contact with the recording medium, whereby there can be provided a reliable and safe cover which will not adversely affect the recording medium.
By adopting such a design for making it difficult for ink droplets to adhere to the surfaces of the recording heads, the frequency of the contact of the cleaning member with the recording heads can be decreased and the water repelling agent of the surfaces of the heads can be prevented from peeling and/or the surfaces of the heads can be prevented from being harmed.